1. Field of the Invention
The present invention relates to an electrical connector and more specifically to a narrow pitch electrical connector in which a plurality of contact pieces is juxtaposed to each other.
2. Description of the Related Art
An exemplary structure of a conventional electrical connector 900 will be explained first with reference to FIG. 1. Such an electrical connector is disclosed in Japanese Patent Application Laid-Open Nos. H11-251005 and 2004-158288 for example.
The electrical connector 900 includes a plurality of first contact pieces 910, a plurality of second contact pieces 920 not shown in FIG. 1, a contact supporting body 930 for holding the first and second contact pieces 910 and 920 and a lead supporting body 940 for holding leads 990.
<Contact Supporting Body>
As shown in FIGS. 2 and 3, the contact supporting body 930 formed of a single piece includes a body portion 931 in the form of a rectangular parallelepiped having a space portion 937 opened to the outside and a slot forming portion 932 in the form of a rectangular parallelepiped having two kinds of slots, i.e., a plurality of first slots 938a and a plurality of second slots 938b. The first and second slots 938a and 938b are alternately disposed in parallel at equal intervals. The respective slots 938a and 938b communicate with each other by a gap portion 936 opened to the outside. An inner wall 937b of the space portion 937 has linear grooves 937a that correspond to the respective slots 938a and 938b. The respective grooves 937a extend in an outside direction. The respective slots 938a and 938b communicate with the space portion 937 within the contact supporting body 930. The slot forming portion 932 is provided with concave portions 932b at both ends thereof. The first contact pieces 910 are inserted into the first slots 938a and the second contact pieces 920 are inserted into the second slots 938b, respectively. The first and second contact pieces 910 and 920 will be referred to simply as contact pieces hereinafter when they need not to be distinguished.
<First Contact Piece>
FIG. 4A is a front view of the first contact piece 910 and FIG. 4B is a side view thereof. In order to explain the first contact piece 910, a first contact plate 910c having a thin and long plate-like shape shown in FIG. 4C will be explained first. The first contact plate 910c formed of a single piece includes a body portion 911 of an L-shaped thin plate, an arm portion 912 of thin and long plate and a leg portion 913c of a thin and rectangular plate.
The arm portion 912 extends from one end portion of the body portion 911, and one end portion 912a of the arm portion 912 is widened. The leg portion 913c extends from the other end portion of the body portion 911. In the first contact plate 910c illustrated in the figure, a height H0 of the arm portion 912 near the other end portion thereof is lower than a height H1 of the body portion 911 around a boundary between the arm portion 912 and the body portion 911. A height H2 of a transition region from the leg portion 913c to the body portion 911 is higher than the height H1.
The first contact piece 910 shown in FIGS. 4A and 4B has a three-dimensional shape acquired by bending the leg portion 913c of the first contact plate 910c at a right angle. FIGS. 4A and 4B illustrate the shape thereof acquired by bending the leg portion 913c of the first contact plate 910c in a direction of the front side of the figure. The leg portion 913c of the first contact plate 910c corresponds to the leg portion 913 of the first contact piece 910.
<Second Contact Piece>
FIG. 5A is a front view of the second contact piece 920 and FIG. 5B is a side view thereof. In order to explain the second contact piece 920, a second contact piece plate 920c having a thin and long plate-like shape shown in FIG. 5C will be explained first. The second contact plate 920c formed of a single piece includes a body portion 921 of an L-shaped thin plate, an arm portion 922 of a thin and long plate and a leg portion 923c of a thin and rectangular plate. The arm portion 922 of the second contact plate 920c has the same shape with the arm portion 912 of the first contact plate 910c. The leg portion 923c of the second contact plate 920c has the same shape with the leg portion 913c of the first contact plate 910c. The body portion 921 of the second contact plate 920c has a shape obtained by turning the body portion 911 of the first contact plate 910c upside down.
The arm portion 922 extends from one end portion of the body portion 921, and one end portion 922a of the arm portion 922 is widened. The leg portion 923c extends from the other end portion of the body portion 921. In the second contact plate 920c illustrated in the figure, a height H0 of the arm portion 922 near the other end portion thereof is lower than a height H1 of the body portion 921 around a boundary between the arm portion 922 and the body portion 921. A height H2 of a transition region from the leg portion 923c to the body portion 921 is higher than the height H1. The respective heights H0, H1 and H2 shown in the figure of the second contact plate 920c are equal to those heights H0, H1 and H2 shown in the figure of the first contact plate 910c. 
A difference of the second contact plate 920c from the first contact plate 910c is that while the leg portion 913c is provided at one side of a direction orthogonal to a longitudinal direction of the contact piece in the first contact plate 910c, the leg portion 923c is provided on the other side of the direction in the second contact plate 920c. 
The second contact piece 920 shown in FIGS. 5A and 5B has a three-dimensional shape obtained by bending the leg portion 923c of the second contact plate 920c at a right angle. FIGS. 5A and 5B illustrate the shape thereof acquired by bending the leg portion 923c of the second contact plate 920c in the direction of the front side of the figure. The leg portion 923c of the second contact plate 920c corresponds to the leg portion 923 of the second contact piece 920.
<Inserting Contact Pieces>
As shown in FIG. 2, each of the first contact pieces 910 is inserted into the corresponding first slot 938a of the contact supporting body 930 with the arm portion 912 thereof in the lead. Each of the first contact pieces 910 is inhibited from excessively entering the contact supporting body 930, the leg portion 913 thereof contacting the slot forming surface 935 of the slot forming portion 932. The grooves 937a in the space portion 937 guide the arm portions 912 to store in the space portion 937.
Similarly, each of the second contact pieces 920 is inserted into the corresponding second slot 938b of the contact supporting body 930 with the arm portion 922 thereof in the lead. Each of the second contact pieces 920 is inhibited from excessively entering the contact supporting body 930, the leg portion 923 thereof contacting the slot forming surface 935 of the slot forming portion 932. The grooves 937a in the space portion 937 guide the arm portions 922 to store in the space portion 937.
The respective contact pieces are held so that insulation between the adjacent contact pieces is kept within the contact supporting body 930. Still more, an inner wall 939 of the contact supporting body 930 isolates the body portions of the adjacent contact pieces. FIG. 2 shows in a lower part of figure a construction in a state in which the first contact pieces 910 are inserted into the first slots 938a and the second contact pieces 920 are inserted into the second slots 938b. As shown in the figure, the leg portions 913 of the first contact pieces 910 are arrayed in a row in an upper deck of the contact supporting body 930 and the leg portions 923 of the second contact pieces 920 are arrayed in a row in a lower deck. In this state, the first contact pieces 910 and the second contact pieces 920 are arrayed in parallel so that the arm portions 912 and 922 overlap each other when the contact supporting body 930 is seen from the side (see FIG. 7).
<Lead Supporting Body>
FIG. 6A is a perspective view of the lead supporting body 940 and FIG. 6B is a back view thereof. The lead supporting body 940 formed of a single piece includes a body portion 945 in which a lead holding portion 941 having a plurality of grooves 941a into which the leads 990 are fitted is formed in a double-deck structure, two clip portions 943 extending from both ends of the body portion 945 in an extension direction of the grooves 941a and a plate-like table portion 942 extending from a center part 940b of the body portion 945. The two clip portions 943 extend in the same direction. An end of each clip portion 943 is bifurcated, and catch portions 943b are formed at the bifurcated ends. The table portion 942 is provided on the same side with the side where the respective clip portions 943 are provided. Part of the table portion 942 is tapered toward an end of each clip portion 943. This plays a role of leading the leg portions of the respective contact pieces toward the front of the lead holding portion 941 in assembling the lead supporting body 940 into the contact supporting body 930.
<Assembling Contact Supporting Body with Lead Supporting Body>
The lead supporting body 940 is assembled into the contact supporting body 930 as shown in FIG. 1. The clip portions 943 of the lead supporting body 940 fit into the concave portions 932b of the contact supporting body 930, and the catch portions 943b of the lead supporting body 940 catch on the slot forming portion 932 due to elasticity of the clip portions 943. It prevents the lead supporting body 940 from being disengaged from the contact supporting body 930. In the state in which the lead supporting body 940 is assembled with the contact supporting body 930, the leg portions 913 of the first contact pieces 910 are placed upon an upper surface of the table portion 942 of the lead supporting body 940 and leg portions 923 of the second contact pieces 920 are placed under an under surface (not shown in FIG. 1) of the table portion 942. Leads 990 are fitted into the grooves 941a of the lead holding portion 941, and each of the grooves 941a holds one lead 990. An unwrapped core portion 990b of each of the leads 990 is soldered to the leg portion 913 or 923 corresponding to the groove 941a. 
The electrical connector is required to be miniaturized depending on their use. Consider here to lower a height of the lead supporting body 940. The height L0 (see FIG. 6B) of the lead supporting body 940 is a total of a height of the lead holding portion 941 with double-deck structure including the center part 940b of the body portion 945. The height of the lead holding portion 941 depends on outer diameters of the leads 990. It is then difficult to freely design and lower the height of the lead holding portion 941 because the outer diameter of the lead 990 is standardized in general. Meanwhile, the height of the center part 940b is determined by a distance L1 between the leg portions 913 and 923 as shown in FIG. 7. That is, the height of the lead supporting body 940 may be lowered by reducing the distance L1.